|Zu sp. |
in Martin & Hilton, 2021.
photographed in Nusa Penida, Indonesia by Helen Mitchell
The family Trachipteridae—the Ribbonfishes, Dealfishes, and their relatives—has a circumglobal distribution, with at least 10 species in three genera (Zu Walters & Fitch 1960, Desmodema Walters & Fitch 1960, and Trachipterus Goüan 1770) that are characterized by elongate, extremely laterally compressed bodies, large eyes, absence of ribs, spines on lateral-line scales, greatly protrusible mouths, and a lack of pelvic fins in adults. They are also known for the drastic morphological changes that occur during ontogeny. Trachipterids are poorly represented in collections due to the fragile nature of their bodies. Most studies of the Trachipteridae have been limited by the numbers, developmental stages, and the completeness of the specimens that were examined. Along with the lack of available material, incomplete and conflicting character information compounds the taxonomic confusion of Trachipteridae. Despite the body of regional revisions that have examined trachipterid taxonomy, none have synthesized a suite of morphological characters across ontogeny. The goals of this paper are to (1) revise the family Trachipteridae, (2) revise the genera Trachipterus, Zu, and Desmodema, including information regarding ontogeny and biogeography, and 3) address the alpha taxonomy of Zu, Desmodema, and Trachipterus from the western Pacific Ocean. We recognize possibly five species of Trachipterus as being present in the western Pacific, as well as two species of both Zu and Desmodema. Despite additions to the specimen base that allows refinement of taxonomy and diagnoses, there are still large knowledge gaps associated with the taxonomic review of Trachipteridae. These reflect incomplete understanding of geographic distribution of taxa which may mask unrecognized taxonomic variability. The genus Trachipterus specifically remains problematic and will require greater detailed global study. Early life history stages remain unknown for several taxa which hinders full interpretation of ontogenetic transitions. Protracted transitions, some of which are clarified here, further confuse stage-based diagnoses and must be considered in future analyses of this family.
Keywords: Pisces, Ribbonfishes, Trachipterus, Desmodema, Zu, ontogenetic characters
Order Lampridiformes Goodrich 1909
Family Trachipteridae Swainson 1839
Trachipterus Goüan 1770
Putatively valid taxa in the western Pacific Ocean
1. Trachipterus trachypterus (Gmelin 1789). Holotype: No types known. Mediterranean.
2. Trachipterus altivelis Kner 1859. Syntype: NMW 22046. Valparaiso, Chile. Unavailable for examination in current study.
3. Trachipterus arawatae Clarke 1881. Holotype NMNZ P.1008, 51 cm SL. Hominy Cove, Jackson’s Bay New Zealand. Examined.
4. Trachipterus jacksonensis (Ramsay 1881). Syntype: AMS A.9114, 1408 mm, caudal missing (736 mm SV). Manly Beach, Port Jackson, New South Wales, Australia. Examined.
5. Trachipterus ishikawae Jordan & Snyder 1901. Holotype: NSMT 589, 1250 mm SL. Off the mouth of Tokyo Bay, between Misaki and Boshu. Examined.
|Zu sp. Live specimen (not collected) photographed in Mallorca, Spain. |
photo: Michael Makowiecki.
|Zu sp. Live specimen (not collected) photographed in Nusa Penida, Indonesia.|
photo: Helen Mitchell.
Zu Walters & Fitch 1960
Zu cristatus (Bonelli 1820)
Zu elongatus Heemstra & Kannemeyer 1984
Desmodema Walters & Fitch 1960
Desmodema polystictum (Ogilby 1898)
Desmodema lorum Rosenblatt & Butler 1977
Despite advances in the understanding of Trachipteridae resulting from tremendous additions to the specimen base, which have allowed for the refinement of the taxonomy and diagnoses within the family, there are still large knowl-edge gaps associated with the taxonomy of the family. These reflect incomplete understanding of geographic dis-tribution of taxa that may mask unrecognized taxonomic variability. The genus Trachipterus specifically remains problematic and will require greater detailed global study. Early life history stages remain unknown for several taxa, which hinders full interpretation of ontogenetic transitions. Protracted transitions, some of which are clarified here, further confuse stage-based diagnoses and must be considered in future analyses of this family.